The data referred to in this question were collected from several sales districts across the country.The data represent sales for a maker of asphalt roofing shingles.Information on the following variables is available. 
Partial SPSS regression output of a multiple regression model with sales as the response variable and the other four variables as predictor variables are given below. 
How many districts were sampled in all?
Definitions:
Respiration
The physiological process of inhaling oxygen and exhaling carbon dioxide from the body, essential for maintaining life.
Hypnosis
A trance-like state of focused attention and heightened suggestibility, often used for therapeutic purposes.
Suggestible
The quality of being inclined to accept and act on the suggestions of others, often leading to increased susceptibility to influence.
Relaxed State
A relaxed state refers to a condition of reduced stress and tension, characterized by calmness and mental, physical, and emotional well-being.
Q26: Which of the following statements about the
Q31: A random sample of size 25 was
Q43: The statistical model for linear regression can
Q53: A sample of employees of a large
Q55: The stemplot below displays data from 30
Q62: The World Malaria Report (2008)has information on
Q64: To investigate whether or not sending text
Q78: Below is a data set with information
Q80: Suppose we are given the following information:
Q219: When one is first acquiring a response,learning